Communication apparatus, integrated circuit, and communication method

ABSTRACT

In communication method for communicating via a transmission channel to which first communication apparatuses communicating based on a first communication system, second communication apparatuses communicating based on a second communication system, and third communication apparatuses communicating based on a third communication system are connected, a data transmission domain and a notification domain for notifying a data transmission within the data transmission domain are allocated to the first communication apparatuses, the second communication apparatuses, and the third communication apparatuses, respectively. In the communication method, notices of the data transmission for each of the first communication apparatuses, the second communication apparatuses and the third communication apparatuses are transmitted within the notification domain, and the data transmission domain is reallocated in accordance with the notices transmitted from the first, second and third communication apparatuses.

This is a continuation application of application Ser. No. 12/249,109filed Oct. 10, 2008, which is based on Japanese Application No.2007-266950 filed Oct. 12, 2007, the entire contents of each of whichare incorporated by reference herein.

BACKGROUND

1. Technical Field

The present invention is related to a communication apparatus, acommunication method, a circuit module and an integrated circuit, whichperform multi-carrier communication operations among a plurality ofcommunication apparatuses, while these communication apparatuses areconnected to a transmission channel and share a communication band.

2. Background Art

Since transmission systems such as the OFDM (Orthogonal FrequencyDivision Multiplexing) system using a plurality of sub-carriers havesuch a great merit that high quality communications can be carried outeven in a severe transmission channel, these transmission systems areutilized not only is wireless communications, but also in wiredcommunications such as power line communications. Generally speaking,frequency bands from 2 MHz to 30 MHz are used as the frequency bands ofthe power line communications (refer to, for example, Patent Publication1). In addition, technical ideas capable of utilizing broadband coveringhigher frequency bands than the above-described frequency band arerecently considered.

Also, other technical ideas capable of equalizing levels of timewaveforms in order not produce peaks and capable of suppressinginterference and the like are proposed in multi-carrier communicationswith employment of a plurality of sub-carriers. In the above-describedpeak suppressing technical ideas, in such a case that a large peak isnot present in time waveforms, phases of respective sub-carriers arerotated by using a default phase vector, whereas in such a case that alarge peak may be monitored, a phase vector is changed so as to searchsuch a phase vector by which the peak is not produced. Then, the phasesof the respective sub-carriers are rotated by the searched phase vector(refer to, for example, Non-patent Publication 1). In multi-carriercommunications, such peak suppressing technical ideas constituteessential techniques to decrease a difficulty in design of poweramplifiers.

In the case that a plurality of different logic networks are formed byemploying communication apparatuses such as power line communicationapparatuses connected to transmission channels, security among thesedifferent networks is maintained by employing network keys and the like.In general, technical specifications of these communication apparatusesconnected to the respective networks are identical to each other. Inother words, phase vectors which are employed in order to suppress peaksare also identical to each other. With employment of the above-describedtechnical ideas, even among the networks which are different from eachother in physical layer levels of communication apparatuses, signals ofthe respective networks can be sensed (carrier sensing is available); ifthe CSMA (Carrier Sense Multiple Access) technique and the like areutilized, then it is possible to suppress collisions of signals; andeven when the different networks are present relatively close to eachother, communications can be smoothly carried out.

The technical idea described in the Patent Publication 1 has thefollowing purpose: That is, even in such a case that the plural sorts ofcommunication apparatuses whose communication systems are different fromeach other are connected to the shared transmission channel, thecollisions of the signals are avoided without executing the demodulatingprocess operation and the like which may cause relatively heavy loads,and signals outputted from other communication apparatuses can bereadily sensed. In accordance with this technical idea, such a conditionfor indicating whether or not a communication request signal of acontrol period is present may change a slot allocation of a date periodsubsequent to the control period. Then, since a communication requestsignal is rotated by a phase vector, the communication request signalcan be firmly sensed. However, a detailed description is not made of aslot allocation of a data domain. Thus, in this technical idea, thereare some possibilities that data capable of satisfying a required delaytime cannot be firmly transmitted.

[Patent Publication 1] JP-A-2007-135180

[Non-patent Publication 1] Denis J. G. Mestdagh and Paul M. P. Spruyt,“A Method to Reduce the Probability of Clipping in DMT-BasedTransceivers”, IEEE Transactions on Communications, Volume 44, No. 10,pages 1234 to 1238, in 1996

SUMMARY

The present invention has been made to solve the above-describedproblems, and therefore, has an object to provide a communicationapparatus, a communication method, a circuit module and an integratedcircuit, by which even when plural sorts of communication apparatuseswhose communication systems are different from each other are connectedto a shared transmission channel, while limit of delays in response todata which are tried to be transmitted by the respective communicationapparatuses can be satisfied, signals can be transmitted in a higherefficiency by avoiding collisions of signals. Also, another object ofthe present invention is to provide a communication method, acommunication apparatus and a communication system, which are capable ofreducing processing workloads for allocating slots executed by thecommunication apparatuses in order to avoid collisions of the signals.

According to the invention, there is provided a communication apparatusfor communicating based on a first communication system, via atransmission channel to which a first other communication apparatuscommunicating based on the first communication system, second othercommunication apparatuses communicating based on a second communicationsystem, and third other communication apparatuses communicating based ona third communication system are connected, wherein a data transmissiondomain and a notification domain for notifying a data transmissionwithin the data transmission domain are allocated to the communicationapparatus and the first other communication apparatus, the second othercommunication apparatuses, and the third other communicationapparatuses, respectively,

-   -   the communication apparatus, including:    -   a detector which detects a notice transmitted from the first,        second and third other communication apparatuses within the        notification domain;    -   a transmitter which transmits a notice for the data transmission        within the notification domain; and    -   a controller which reallocates the data transmission domain in        accordance with the notice transmitted from the first, second        and third other communication apparatuses and the notice        transmitted from the transmitter.

According to the invention, there is provided a communication method ofa communication apparatus for communicating based on a firstcommunication system, via a transmission channel to which a first othercommunication apparatus communicating based on the first communicationsystem, second other communication apparatuses communicating based on asecond communication system, and third other communication apparatusescommunicating based on a third communication system are connected,wherein a data transmission domain and a notification domain fornotifying a data transmission within the data transmission domain areallocated to the communication apparatus and the first othercommunication apparatus, the second other communication apparatuses, andthe third other communication apparatuses, respectively,

-   -   the communication method, including:    -   detecting a notice transmitted from the first, second and third        other communication apparatuses within the notification domain;    -   transmitting a notice for the data transmission within the        notification domain; and    -   reallocating the data transmission domain in accordance with the        notice transmitted from the first, second and third other        communication apparatuses and the notice transmitted from the        transmitter.

According to the invention, there is provided a circuit module of acommunication apparatus for communicating based on a first communicationsystem, via a transmission channel to which a first other communicationapparatus communicating based on the first communication system, secondother communication apparatuses communicating based on a secondcommunication system, and third other communication apparatusescommunicating based on a third communication system are connected,wherein a data transmission domain and a notification domain fornotifying a data transmission within the data transmission domain areallocated to the communication apparatus and the first othercommunication apparatus, the second other communication apparatuses, andthe third other communication apparatuses, respectively,

-   -   the circuit module, including:    -   a coupler for interfacing with the transmission channel;    -   a detector which detects a notice transmitted from the first,        second and third other communication apparatuses within the        notification domain via the coupler;    -   a transmitter which transmits a notice for the circuit module        within the notification domain; and    -   a controller which reallocates the data transmission domain in        accordance with the notice transmitted from the first, second        and third other communication apparatuses and the notice        transmitted from the transmitter.

According to the invention, there is provided an integrated circuit of acommunication apparatus for communicating based on a first communicationsystem, via a transmission channel to which a first other communicationapparatus communicating based on the first communication system, secondother communication apparatuses communicating based on a secondcommunication system, and third other communication apparatusescommunicating based on a third communication system are connected,wherein a data transmission domain and a notification domain fornotifying a data transmission within the dais transmission domain areallocated to the communication apparatus and the first othercommunication apparatus, the second other communication apparatuses, andthe third other communication apparatuses, respectively,

-   -   the integrated circuit, including:    -   a detector which detects a notice transmitted from the first,        second and third other communication apparatuses within the        notification domain via a coupler for interfacing with the        transmission channel;    -   a transmitter which transmits a notice for the data transmission        within the notification domain via the coupler; and    -   a controller which reallocates the data transmission domain in        accordance with the notice transmitted from the first, second        and third other communication apparatuses and the notice        transmitted from the transmitter.

According to the invention, there is provided a communication method forcommunicating via a transmission channel to which first communicationapparatuses communicating based on a first communication system, secondcommunication apparatuses communicating based on a second communicationsystem, and third communication apparatuses communicating based on athird communication system are connected, wherein a data transmissiondomain and a notification domain for notifying a data transmissionwithin the data transmission domain are allocated to the firstcommunication apparatuses, the second communication apparatuses, and thethird communication apparatuses, respectively,

-   -   the communication method, including:    -   transmitting notices of the data transmission for each of the        first communication apparatuses, the second communication        apparatuses and the third communication apparatuses within the        notification domain; and    -   reallocating the data transmission domain in accordance with the        notice transmitted from the first, second and third        communication apparatuses.

According to the invention, even when plural sorts of communicationapparatuses whose communication systems are different from each otherare connected to a shared transmission channel, while limit of delays inresponse to data which are tried to be transmitted by the respectivecommunication apparatuses can be satisfied, signals can be transmittedin a higher efficiency by avoiding collisions of signals. Also, it ispossible to provide a communication apparatus for reducing processingworkloads for allocating slots executed by the communication apparatusesin order to avoid collisions of the signals.

BRIEF DESCRIPTION OF THE DRAWINGS

The above objects and advantages of the present invention will becomemore apparent by describing in detail preferred exemplary embodimentsthereof with reference to the accompanying drawings, wherein likereference numerals designate like or corresponding parts throughout theseveral views, and wherein:

-   -   FIG. 1 is a diagram for schematically showing an example of an        arrangement of a power line communication system for realizing a        communication method and a communication system of the present        invention;

FIGS. 2A and 2B are diagrams for representing outer appearances of a PLCmodem according to an embodiment of the present invention;

FIG. 3 is a block diagram tor indicating one example as to hardware ofthe PLC modem according to the embodiment of the present invention;

FIG. 4 is a block diagram for indicating another example as to hardwareof the PLC modern according to the embodiment of the present invention.

FIG. 5 is a diagram for showing one example as to a communication cyclein the power line communication system according to the embodiment ofthe present invention;

FIGS. 6A and 6B are diagrams for indicating examples as to a controlsignal domain in the power line communication system according to theembodiment of the present invention;

FIG. 7 is a diagram for indicating another example as to a controlsignal domain in the power line communication system according to theembodiment of the present invention;

FIG. 8 is a diagram for indicating another example as to a controlsignal domain in the power line communication system according to theembodiment of the present invention;

FIG. 9 is a diagram for indicating another example as to a controlsignal domain in the power line communication system according to theembodiment of the present invention;

FIG. 10 is a diagram for showing one example as to an allocation of dataslots in the power line communication system according to the embodimentof the present invention;

FIG. 11 is a diagram for representing one example as to notificationsignals in the power line communication system according to theembodiment of the present invention;

FIG. 12 is a diagram for showing one example as to notification signalsand data slots in the power supply communication system according to theembodiment of the present invention;

FIG. 13 is a diagram for showing another example as to notificationsignals and data slots in the power supply communication systemaccording to the embodiment of the present invention;

FIG. 14 is a diagram for showing another example as to notificationsignals and data slots in the power supply communication systemaccording to the embodiment of the present invention;

FIG. 15 is a diagram for showing another example as to notificationsignals and data slots in the power supply communication systemaccording to the embodiment of the present invention;

FIG. 16 is a diagram for showing a table indicative of a communicationsystems which is allocated to notification signals and data slots of acontrol cycle “T” in the power line communication system according tothe embodiment of the present invention;

FIG. 17 is a diagram for representing one example as to a binary tablefor indicating whether or not notification signals and data slots of thecontrol cycle “T” can be used in the power line communication systemaccording to the embodiment of the present invention;

FIG. 18 is a diagram for showing another table indicative of acommunication systems which is allocated to notification signals anddata slots of a control cycle “T” in the power line communication systemaccording to the embodiment of the present invention;

FIG. 19 is a diagram for showing another example as to notificationsignals and data slots in the power supply communication systemaccording to another embodiment of the present invention; and

FIG. 20 is a diagram for showing another table indicative of acommunication systems which is allocated to notification signals anddata slots of a control cycle “T” in the power line communication systemaccording to the embodiment of the present invention.

DETAILED DESCRIPTION

Referring now to drawings, a description is made of various embodimentsof the present invention. It should be understood that although both apower line communication apparatus and a power line communication systemwill be exemplified in the below-mentioned descriptions, the presentinvention may be similarly applied to other communication apparatusesand other communication systems such as wireless LANs (Local AreaNetworks).

FIG. 1 is a diagram for schematically showing one example as to anarrangement of a power line communication system which realizes thecommunication method and the communication system, according to anembodiment of the present invention. The power line communication systemof FIG. 1 is equipped with a plurality of PLC (Power Line Communication)modems 10A1, 10A2, 10B1, 10B2, 10C1, 10C2, and 10C3, which are connectedto a power line 1A. In the below-mentioned descriptions, when individualPLC modems are referred to, the PLC modems 10A1, 10A2, 10B1, 10B2, 10C1,10C2, and 10C3 are described respectively, whereas when a PLC modem isgenerally referred to, a PLC modem 10 is simply described.

In FIG. 1, the power line 1A is illustrated by employing a single line.However in an actual case, the power line 1A is made of two, or morepieces of conducting lines, and the PLC modem 10 is connected to twoconducting lines among these conducting lines.

As will be later described in detail, the PLC modems 10 contain LANmodular jacks such as RJ45. A telephone set 51 equipped with a displaydevice, a door interphone 52, televisions (TV) 53 and 56, a video server54, a personal computer (PC) 55, and a broadband router (BB rooter) 57are connected to these modular jacks, while the broadband router 57 isconnected to the Internet 58.

The PLC modems 10A1, 10A2, 10B1, 10B2, 10C1, 10C2, and 10C3, whichconstitute the power line communication system of FIG. 1, performcommunication operations based upon three different sorts ofcommunication systems, namely, the PLC modems 10A1 and 10A2 performcommunication operations based upon a communication system “A”; the PLCmodems 10B1 and 10B2 perform communication operations based upon acommunication system “B”; and the PLC modems 10C1, 10C2 and 10C3 performcommunication operations based upon a communication system “C.” Itshould be understood that although the above-described communicationsystems “A” to “C” indicate various sorts of specifications such asprotocols, modulation systems, and frequency bands, these communicationsystems “A” to “C” correspond to the same communication systems in viewof such an operation that the multi-carrier communication of the OFDM(Orthogonal Frequency Division Multiplexing) system is carried out.Since the power line communication system corresponds to one example ofcommunication systems capable of realizing the communication systemaccording to the present invention, other communication systems such aswireless LANs may be alternatively employed in order to realize theabove-described communication method.

Next, a concrete structural example of the PLC modem 10 is shown inFIG. 1. FIGS. 2A and 2B are diagrams for illustratively showing outerappearances of a PLC modem 10; concretely speaking, FIG. 2A is an outerappearance perspective view for representing a front plane of this PLCmodem 10; and FIG. 2B is a rear view of the PLC modem 10. The PLC modem10 shown in FIG. 2 contains a housing 100, and an indicator 23 isprovided on a front plane of the housing 100. As indicated in FIG. 2A,the indicator 23 is constituted by LEDs (Light Emitting Diodes) 23A, 23Band 23C. Also, as represented in FIG. 2B, a power supply connector 21and a LAN (Local Area Network) modular jack 22 such as RJ45 are providedon a rear plane of the housing 100. A power supply cable 1B is connectedto the power supply connector 21; and a LAN cable (which is notindicated in FIG. 2) is connected to the modular jack 23. It should alsobe understood that while a D-Sub (D-subminiature) connector may beprovided in the PLC modem 10, a D-Sub cable may be alternativelyconnected to this D-Sub connector.

FIG. 3 is a block diagram for representing one example as to hardware ofthe PLC modem 10. As shown in FIG. 3, the PLC modem 10 is equipped witha circuit module 30 and a switching power supply 20. The switching powersupply 20 is employed in order to apply various sorts of voltages (forexample, +1.2 V, +3.3 V, and +12 V) to the circuit module 30. Theswitching power supply 20 contains, for example, a switchingtransformer, and a DC/DC converter (both elements are not shown).Electric power is supplied to the switching power supply 20 from a powersupply connector 21 via an impedance upper 27 and an AC/DC converter.

In a circuit module 30, a main IC (integrated circuit) 11, an AFE-IC(Analog Front End IC) 12, a low-pass filter (LPF) 13, a driver IC 15, acoupler 16, a band-pass filter (BPF) 17, a memory 18, an Ethernet PHY-IC(Physical layer-Integrated Circuit) 19, and an AC cycle detector 60 areprovided. The coupler 16 is connected to the power supply connector 21,and is further connected to the power line 1A via the power line 1B, thepower supply plug 25, and an outlet 2. Also, the indicator 23 isconnected to the main IC 11, and a LAN cable 26 is connected to themodular jack 22 in order to be connected to an electric appliance suchas a personal computer. It should also be noted that the main IC 11functions as a communication control unit in such a case that the mainIC 11 performs a power line communication.

The main IC 11 is constituted by a CPU (Central Processing Unit) 11A,PLC-MAC (Power Line Communication/Media Access Control layer) blocks11C1 and 11C2, and PLC-PHY (Power Line Communication/Physical layer)blocks 11B1 and 11B2. The CPU 11A implements a 32-bit RISC (ReducedInstruction Set Computer) processor. The PLC-MAC block 11C2 manages aMAC layer (Media Access Control layer) of a transmission signal, and thePLC-MAC block 11C1 manages a MAC layer of a reception signal. Also, thePLC-PHY block 11B2 manages a PHY layer (Physical layer) of thetransmission signal, and the PLC-PHY block 11B1 manages a PHY layer ofthe reception signal. The AFE-IC 12 is arranged by a D/A converter (DAC)12A, an A/D converter (ADC) 12D, and variable gain amplifiers (VGA) 12Band 12C. The coupler 16 is constituted by a coil transformer 16A andcoupling capacitors 16B and 16C. It should also be understood that theCPU 11A controls operations of the PLC-MAC blocks 11C1, 11C2 and thePLC-PHY blocks 11B1, 11B2, and also, controls the entire operations ofthe PLC modem 10 by utilizing data stored in the memory 18.

In FIG. 3, while the PLC-MAC blocks 11C1 and 11C2 and the PLC-PHY blocks11B1 and 11B2 are provided to be employed for transmission andreception, respectively. Alternatively, while a PLC-MAC block 11C and aPLC-PHY block 11B (not shown) may be provided to share in transmissionand reception operations.

Similar to a general modem, the main IC 11 is an electric circuit (LSI)which performs signal process operations including a basic controloperation and modulating/demodulating operations so as to execute datacommunication operations. In other words, the main IC 11 modulatesreception data outputted from a communication terminal such as a PC(Personal Computer), and then, outputs the modulated data as atransmission signal (transmission data) to the AFE-IC 12. Further, themain IC 11 demodulates a signal which is inputted from the side of thepower line 1A via the AFE-IC 12, and then, outputs the demodulatedsignal as a reception signal to the communication terminal such as thePC.

The AC cycle detector 60 produces such a synchronization signal which isrequired in order that the respective PLC modems 10 execute controloperations at common timing. The AC cycle detector 60 is arranged by adiode bridge 60 a, resistors 60 b and 60 c, a DC power supply unit 60 e,and a capacitor 60 d. The diode bridge 60 a is connected to the resistor60 b. The resistor 60 b is connected series to the resistor 60 c. Boththe resistors 60 b and 60 c are connected parallel to one terminal ofthe capacitor 60 d. The DC power supply unit 60 e is connected to theother terminal of tire capacitor 60 d. Concretely speaking, thesynchronization signal is processed in accordance with thebelow-mentioned manner. That is, the AC cycle detector 60 detects zerocross points of an AC power waveform AC of a commercial power supply,which is applied to the transmission channel 1A, namely, such zero crosspoints of AC voltage waveform constructed of a sine wave having afrequency of 50 Hz, or 60 HZ. Then, the AC cycle detector 60 produces asynchronism signal while the timing for detecting the zero cross pointsis defined as a reference. As one example of the above-describedsynchronisation signal, a rectangular wave may be conceived which isconstituted by a plurality of pulses synchronized with the zero crosspoints of the AC power waveform. The AC cycle detector 60 is notnecessarily required. In this alternative case, the synchronizationamong these PLC modems 10 may be established by employing asynchronization signal contained in a communication signal.

A communication operation by the PLC modem 10 shown in FIG. 3 is roughlycarried out as follows: That is, data inputted from the modular jack 22is supplied via the Ethernet PHY-IC 19 to the main IC 11 and thesupplied data is digitally processed, so that a digital transmissionsignal is produced which is D/A-converted into an analog signal by theD/A converter (DAC) 12A of the AFE-IC 12, and then, the analog signal isoutputted to the power line 1A via the low-pass filter 13, the driver IC15, the coupler 16, the power supply connector 21, the power supplycable 1B, the power supply plug 25, and also, the outlet 2.

A signal received from the power line 1A is supplied via the coupler 16to the band-pass filter 17, and then, a gain of the supplied signal isadjusted by the variable gain amplifier (VGA) 12C of the AFE-IC 12.Thereafter, the gain-adjusted signal is A/D-converted by the A/Dconverter (ADC) 12D into a digital signal, and then, the digital signalis supplied to the main IC 11 so as to be digitally processed, so thatthe inputted analog signal is converted into the digital data. Then,this digital data is outputted via the Ethernet PHY-IC 19 from themodular jack 22.

FIG. 4 is a block diagram for showing another example as to the hardwareof the PLC modem 10. As represented in FIG. 4, a PLC modem 10 containstwo sets of hardware used to perform communication process operations,and other arrangements identical to the arrangements of the PLC modem 10shown in FIG. 3. That is, while the PLC modem 10 of FIG. 4 contains botha circuit module 30 and a switching power supply 20, a power supplyvoltage is applied from the power supply connector 21 via the impedanceupper 27 and the AC/DC converter 24 to the switching power supply 20.

A circuit module 30 is equipped with one hardware which is arranged by amain IC (Integrated Circuit) 31, an AFE-IC (Analog Front End/IntegratedCircuit) 32, a low-pass filter (LPF) 33, and a driver IC 35 in order toperform one set of a communication process operation. The circuit module30 is further equipped with another hardware which is arranged by asub-IC 41, an AFE-IC 42, a low-pass filter 43, and a driver IC 45 inorder to perform one set of a communication process operation. Since twosets of the above-described hardware are basically identical to theabove-described main IC 11, AFE-IC 12, low-pass filter 13, and driver IC15 of the PLC modem 10 shown in FIG. 3, detailed descriptions thereofwill be omitted. Also, such a technical structure that a coupler 16, aband-pass filter (BPF) 17, a memory 18, and a Ethernet PHY-IC 19 areprovided in the PLC modem 10 of FIG. 4 is identical to that of the PLCmodem 10 of FIG. 3. The main IC 31 may also function a communicationcontrol operation in such a case that a power line communicationoperation is carried out. Also, the memory 48 stores thereinto datawhich is used by the sub-IC 41.

The power line communication system indicated in FIG. 3 performs acommunication operation by such a manner that the PLC modem 10 connectedto the power line 1A transmits a control signal for controllingcommunication operations among the PLC modems 10 within a control signaldomain, and also, transmits data within a data signal domain subsequentto the above-described control signal domain. A signal domain forcombining one control signal domain with a data signal domain subsequentto this control signal domain will be referred to as a communicationcycle. As a consequence, a control signal domain is present at a head ofeach of these communication cycles.

A data signal domain corresponds to a time domain in which a pluralityof control cycles are continuously provided, while each of therespective control cycles contains a plurality of data slots. A dataslot corresponds to such a time domain that data supplied from aspecific PLC modem are grouped, and then, the grouped data istransmitted. Since a control signal domain is provided at a head of acommunication cycle, both a control cycle of the head of thecommunication cycle, and a head data slot of the head control cycle aremade short by the control signal domain. A data slot is a data slotformed by the TDM (Time Division Multiplexing) system, and however, maycontain a data slot formed by the FDM (Frequency Division Multiplexing).

A control signal which is transmitted within a control signal domaincontains such a notification signal within a data signal domainsubsequent to this control signal domain, while the notification signalnotifies that data is transmitted from a PLC modem which has transmittedthe above-described control signal. Within a data signal domain after anotification signal is transmitted, a data signal is transmitted fromthe PLC modem which has transmitted the above-described notificationsignal by a plurality of data slots which uniquely correspond to atleast this notification signal. The data slots which uniquely correspondto the notification signal contains a plurality of data slots among dataslots which constitute each of control cycles, so that data from a PLCmodem are transmitted without having a large interval within a datasignal domain. As a consequence, while limits of delays in response todata which are tried to be transmitted by the respective communicationapparatuses can be satisfied, data signals can be transmitted in ahigher efficiency by avoiding collisions of data signals.

FIG. 5 represents one example of a communication cycle conducted in thepower line communication system according to the embodiment of thepresent invention. A single communication cycle “H” is constituted by aplurality (namely, 8 pieces) of control cycles “T0” to “T7” (refer to(a) in FIG. 5), and each of control cycles “T” is constituted by aplurality (namely, 10 pieces) of data slots “S0” to “S9” (refer to (b)in FIG. 5). A head portion of the head data slot “S0” of the controlcycle “T0” is secured as a control signal domain “C.” As a result, thisdata slot “S0” is made slightly narrower, as compared with other dataslots.

In the example of FIG. 5, a control cycle “T” corresponds to two timeperiods (namely, 40 msec in case of 50 Hz) of the power supply, and acommunication cycle “H” corresponds to 40*8=320 msec. Also, a width of asingle data slot corresponds to 40/10=4 msec.

The control signal domain “C” corresponds to a time domain which isprovided at a head of a communication cycle “H”, and contains at least anotification signal domain “R” during which the above-describednotification signal is transmitted (refer to (e) in FIG. 5). In theexample of (c) in FIG. 5, while the notification signal domain “R”contains three request slots, the respective request slots are providedin order to transmit a notification signal “ΦA” of the communicationsystem “A”, a notification signal “ΦB” of the communication system “B”,and a notification signal “ΦC” of the communication system “C.” A widthof each of the request slots is, tor example, 80 μsec. A guard time of80 μsec is provided before and after each of the request slots. As aconsequence, the notification signal domain “R” of FIG. 5 which has thethree request slots is equal to 720 μsec as an entire time.

FIGS. 6A and 6B show detailed contents of the above-described controlsignal domain “C.” As indicated in FIGS. 6A and 6B, a control signal isa multi-carrier signal which utilizes a plurality of sub-carriers havingfrequencies from 2 MHz to 30 MHz, and corresponds to such a signal thatknown data (for example, all of data are “1”) are rotated by apredetermined phase vectors. A rotating process operation based upon aphase vector may be carried out by the PLC-PHY blocks of FIG. 3 and FIG.4, for instance, as shown in the Patent Publication 1, so thatdescriptions thereof will be omitted. Also, as will be discussed later,a notification signal of the control signal domain “C” is utilized so asto determine a data transmission slot, and also, a detection of acontrol signal is also carried out by the PLC-PHY blocks. It should alsobe understood that in such a PLC modem (namely, PLC modems 100 of FIG. 3and FIG. 4) equipped with a plurality of PLC-PHY blocks, a transmissionof a control signal is carried out by one PLC-PHY block (namely, PLC-PHYblock 11B2 shown in FIG. 3, and PLC-PHY block 42D indicated in FIG. 4).As represented in FIGS. 6A and 6B, in such a case that the notificationsignals corresponding to the different communication systems aretransmitted by employing the respective different request slots, suchnotifications which are rotated by the respective different phasevectors may not be used.

FIG. 6A indicates an example having slots which are employed in order totransmit a synchronization signal “S” as a control signal, and also totransmit notification signals “ΦA”, “ΦB”, “ΦC” corresponding to thecommunication systems “A”, “B”, “C”, respectively. FIG. 6B indicatesanother example having slots which are employed in order to transmit thenotification signals, “ΦA”, “ΦB”, “ΦC”, corresponding to thecommunication systems “A”, “B”, “C”, without the synchronization signal“S.” Alternatively, not only the control signal, the synchronizationsignal and the notification signals are transmitted, but also othercontrol signals may be transmitted. Furthermore, with respect to thenotification signals, not only the request slots for transmitting threesorts of the above-described notification signals “ΦA”, “ΦB”, “ΦC” aresecured, but also other request slots for transmitting four sorts, ormore sorts of notification signals may be alternatively secured.

FIG. 7 shows another example as to a control signal domain “C.” In theexample of FIG. 7, only a single notification signal can be transmittedwithin a single control domain “C.” In other words, in communicationcycles “H0” and “H3”, the notification signal “ΦA” corresponding to thecommunication system “A” can be transmitted by request slots allocatedthereto; in a communication cycle “H1”, the notification signal “ΦB”corresponding to the communication system “B” can be transmitted by arequest slot allocated thereto; and, in a communication cycle “H2”, thenotification signal “ΦC” corresponding to the communication system “C”can be transmitted by a request slot allocated thereto. When theabove-described idea of the control signal domain “C” is employed, adecision for decide whether or not a notification signal is present canbe made by merely detecting whether or not a single control signal ispresent within a single control signal domain. As a result, the processfor detecting the notification signal can be simplified, and thearrangement of the communication apparatus can be made simple. It shouldbe understood that, as indicated in FIG. 7, since the communicationsystems “A” to “C” with respect to the respective communication cycles“ΦA” to “ΦC” are allocated in a periodic manner, the defecting processfor the notification signals can be simplified.

FIG. 8 is another example as to notification signals within a controlsignal domain “C” (note that in FIG. 8 and succeeding drawings, onlycommunication cycle “H0” is described). This example of FIG. 8corresponds to such a case that there is one request slot fortransmitting a notification signal corresponding to a communicationsystem, and as to the respective notification signals, such notificationsignals are employed which are rotated by phase vectors different fromeach other. In other words, in communication cycles “H0” and “H3”, thenotification signal “ΦA” corresponding to the communication system “A”is transmitted; in communication cycles “H1” and “H4”, the notificationsignal “ΦB” corresponding to the communication system “B” istransmitted; and in a communication cycle “H2”, the notification signal“ΦC” corresponding to the communication system “C” is transmitted. Whenthe above-described idea of the control signal domain “C” is employed,since only a single notification signal is transmitted within a singlecontrol signal domain, one corresponding phase vector is merely detectedfrom a plurality of different phase vectors within a single controlslot. As a result, the arrangement of the communication apparatus can bemade simple. Also, a control domain can be made narrow, so that acommunication efficiency can be improved. In the above case, since onlyone notification signal is contained in each request slot, low precisionof the AC cycle detector 60 which is provided in the communicationapparatus for receiving the notification signals “ΦA”, “ΦB” and “ΦC”,for detecting the zero-cross point of AC power waveform may be accepted.Accordingly, a low-cost AC cycle detector can be used in this case.

FIG. 9 is another example as to notification signals within a controlsignal domain “C.” That is, in the example of FIG. 9, two sets ofrequest slots are provided which are employed in order to transmitnotifications corresponding to three sorts of communication systems. Inthis example, as to notification signals “ΦA” and “ΦB”, suchnotification signals are employed which are rotated by phase vectorsdifferent from each other. In other words, when both the notificationsignals “ΦA” and “ΦB” are transmitted, this communication systemcorresponds to the above-described communication system “A”, whereaswhen only the notification signal “ΦA”, or the notification signal “ΦB”is transmitted, this communication system corresponds to either thecommunication system “B” or the communication system “C.” In such a casethat both the notification signals “ΦA” and “ΦB” are transmitted, othercommunication systems may be alternatively set based upon a signaltransmission order. For example, when the notification signals ΦA and ΦBare transmitted in this order, TDM of the communication system “A” maybeset, whereas when the notification signals ΦB and ΦA are transmitted inthis order, FDM of the communication system “A” may be set. Withemployment of this notification signal transmission method, even whentransmission slots of notification signals are located adjacent to eachother, the notification signals can be firmly detected, and thecommunication efficiency can be improved by narrowing the control signaldomains. Also, the communication systems can be discriminated from eachother by combining the plurality of notification signals with eachother. As a result, the communication efficiency can be furthermoreimproved by narrowing the control signal domain.

Next, a description is made of such an allocation example that dataslots are allocated within a data signal domain after a notificationsignal is transmitted. FIG. 10 is a diagram for representing one exampleas to an allocation of data slots. In the example of FIG. 10, such adata slot allocation is performed that the PLC modems which utilizethree sorts of the communication systems (communication systems A, B, C)as shown in FIG. 1 are connected to a power line, and furthermore, sucha PLC modem (not shown in FIG. 1) which utilizes a communication system(communication system D) having a low priority performs a communicationoperation at the same time when the first-mentioned PLC modems performcommunication operations. As shown in FIG. 10, in all of control cycles“T” within a single communication cycle “H”, the same data slots areallocated. If these data slots are allocated, then while limits ofdelays in correspondence with data which are tried to be transmitted byrespective communication apparatuses connected to the commontransmission channel can be satisfied, collisions of signals can beavoided, so that data can be transmitted in a high efficiency.

FIG. 10 is such an exemplification that the data slots are allocatedunder such a status that four sorts of notification signals aretransmitted. Alternatively, the notification signals may be transmittedwithin control signal domains of the respective allocated communicationcycles, or may be transmitted within the same control signal domain.FIG. 11 indicates an example as to statues of these notificationsignals. (a) in FIG. 11 shows an example in such a case that thenotification signals are utilized in communication cycles to which threesorts of the communication systems (namely, communication systems, “A”,“B”, “C”) are allocated, and a communication system (communicationsystem “D”) having a low priority is present. In each of thecommunication cycles “H”, the notification signal of the communicationsystem (communication system “D”) having the low priority is transmittedafter the notification signals of the communication systems “A”, “B”,“C”, respectively. Also, (b) in FIG. 11 shows another example in such acase that the notification signals are transmitted within a controldomain in which three sorts of the communication systems (namely,communication systems “A”, “B”, “C”) are identical to each other, acommunication system (communication system “D”) having a low priority ispresent. In each of the communication cycles “H”, the notificationsignal of the communication system (communication system “D”) having thelow priority Is transmitted after the notification signals of thecommunication systems “A”, “B”, “C”. Similar to (a) in FIG. 11, (c) inFIG. 11 shows an example in such a case that the notification signalsare utilized in communication cycles to which three sorts of thecommunication systems (namely, communication systems “A”, “B”, “C”) areallocated, and a communication system (communication system “D”) havinga low priority is present. However, (c) in FIG. 11 shows such a casethat the notification signals of the communication systems “A”, “B”, and“C” are transmitted in accordance with the method represented in FIG. 9.In each of the communication cycles “H”, the notification signals of thecommunication systems A, B, C are transmitted in accordance with themethod shown in FIG. 9 before the notification signal of thecommunication system (communication system “D”) having the low priority.Also, with respect to the communication system (communication system“D”) having the low priority, the notification signal may not always betransmitted within all of the control domains where the notificationsignal can be transmitted. It should also be noted that in this case, aninterval of transmission signals of the communication systems “D” mustbe previously determined. For example, as the predetermined timeinterval, a notification signal of the communication system “D” must betransmitted one time within three control domains.

FIG. 12 indicates data slots In the case that notification signals “ΦA”,“ΦB”, “ΦC”, which correspond to the respective communication systems“A”, “B”, “C” are transmitted within a control signal domain “C” of eachallocated communication cycle “H.” It is so assumed that thenotification signals corresponding to the communication system “D” aretransmitted in all of the communication cycles, as shown in FIG. (a),(b) or (c) in 11. As represented in FIG. 12, when a notification signalcan be transmitted within an allocated communication cycle, such anotification signal corresponding to one communication system iseffective until a communication cycle during which the same notificationsignal can be transmitted at the next time. In other words, withincommunication cycles subsequent to at least the communication cycle“H2”, notification signals corresponding to the communication systems“A”, “B”, “C”, “D” are effective. As a result, similar to FIG. 10, thedata slots are allocated to the communication systems “A”, “B”, “C” and“D.”

FIG. 13 is a diagram for indicating data slots under the same conditionas that of FIG. 11 except that notification signals corresponding to thenotification system “D” are not transmitted. As apparent from FIG. 13,slots from the data slot “S1” up to the data slot “S9” are allocated tothe communication systems “A”, “B”, “C” in a periodic manner. On theother hand, a slot “S0” is allocated to a communication systemcorresponding to such a notification signal which Is transmittedimmediately before this slot “S0.” That is, within a data domain of acommunication cycle “H2” of FIG. 13, the communication system “C”corresponding to the notification which was transmitted immediatelybefore the slot “S0” is allocated to this slot “S0.” Since theabove-described slot allocating method is employed, the respectivecommunication systems “A” to “D” can use the slot “S0” at the sameratio.

FIG. 14 shows another example of data slots. The example of FIG. 14indicates structures of data slots in such a case that a notificationsignal corresponding to the communication system “C” has not beentransmitted within a control signal domain allocated to thecommunication system “C”, namely, in the case that the notificationsignal has not be transmitted within a control signal domain of acommunication cycle “H2” allocated to the communication system “C.” Inthis case, a communication system which is allocated to the data slotsS1, S2, S4, S5, S7, and S8 is the communication system “A” or thecommunication system “B.” The communication systems “A” and “B” arealternately allocated to the remaining data slots S0, S3, S6, and S9. Itshould also be noted that the communication systems are not alwaysallocated to the data slots in the above-described alternate manner, butmay be previously determined by considering system latency, and thelike.

FIG. 15 shows another example of data slots. FIG. 15 represents such acase that only notifies signals corresponding to the communicationsystem “B” are transmitted. In this case, all of the data slots areallocated to this communication system “B.”

As previously described, in such a case that a notification signalcorresponding to a specific notification system is present, data slotsto be allocated in responding to this notification signal contain suchdata slots which are previously and uniquely allocated to the respectivecommunication systems. For instance, in the case that a notificationsignal of the communication system “A” is transmitted, the data slots tobe allocated thereto contains the data slots S1, S4, S7, which areuniquely allocated to the communication system “A”. Also, in the casethat a notification signal of the communication system “B” istransmitted, the data slots to be allocated thereto have contained thedata slots S2, S5, S8, which are uniquely allocated to the communicationsystem “B”. Furthermore, in the case that a notification signal of thecommunication system “C” is transmitted, the data slots to be allocatedthereto have contained the data slots S3, S6, S9, which are uniquelyallocated to the communication system “C”, Then, such data slotsallocated to such communication systems whose notification signals havenot be transmitted are properly allocated to other communication systemswhose notification signals are transmitted. FIG. 16 is a table forindicating notification signals which are present (are transmitted) in atransmission channel, and communication systems which are allocated todata slots of a control cycle “T.” While such a table is previouslystored in the PLC modem 10, a data, slot capable of transmitting data isdetermined based upon a notification signal present in the transmissionchannel, and then, the data is transmitted by using this determined dataslot. For instance, when the own communication system is thecommunication system “A”, while the PLC modem 10 has previously storedthereinto a binary table shown in FIG. 17, the PLC modem 10 may transmitdata by employing a data slot indicative of “1” in accordance withstatuses of other existing systems. Alternatively, while the PLC modem10 has previously prepared all of binary tables corresponding to thecommunication systems “A”, “B”, “C”, the PLC modem 10 may switch thesebinary tables in correspondence with a sequence connected to thetransmission channel. For example, in such a case that another singlecommunication system has already been connected to the transmissionchannel at the time when the own communication system is connected tothe transmission channel, the communication system already connected tothe transmission channel is the communication system “A”; the owncommunication system is the communication system “B”; and thecommunication system which will be thereafter connected is thecommunication system “C.”

It should also be noted that while the present system is not restrictedonly to a total number of these communication systems, the tables areconstructed in accordance with the above-described example inconjunction with the number of communication systems, so that a similareffect may be expected. For example, in such a case that the majorcommunication system is constructed of two systems (namely,communication systems “A” and “B”), it is sufficient to realize such adata slot allocation table as shown in FIG. 18.

As another embodiment of the present invention, a description is made ofsuch a case that each of communication systems holds a plurality oftables with reference to FIG. 19 and FIG. 20. Although only one tablewas held in the above-described embodiment, in the present embodiment,while each of the communication systems holds a plurality of tables, adescription is made how to update the tables by using either tableupdating slots or different phase vectors in response to a total numberof these tables.

In the present embodiment, a slot “X” is added by considering two tables(alternatively, phase vector may be added in order to share otherslots). Such a case that the respective communication systemsalternately transmit notification signals will now be considered. Atthis time, as represented in FIG. 19, since a notification signal “ΦX”is transmitted in a slot “X” within the same control domain as such acontrol domain during which each of the communication systems transmitsa notification signal, such an event that a table to be used is updated(namely, presently used table is switched to another table) is notifiedto another communication system. In other words, in FIG. 19, thecommunication system “B” transmits the notification signal “ΦX” in theslot “X” of the same control domain as the control domain for the ownnotification. In this case, while the communication systems “A”, “B”,“C” are present, approximately 3.3 pieces of slots are normallyallocated to the communication system “B” (“3.3 pieces” is calculated bythat, among 10 pieces of data slots, 3 slots are continuously secured,and S0 slot is secured only 1 time within 3 times of communication cycle“H”). However, in FIG. 19, since the notification signal is transmittedin the slot “X”, it is so assumed that such a fact that, for example,only 2 pieces of slots are used without utilizing approximately 3.3pieces of slots is notified. As previously explained, a slot is providedwithin the same control domain as the control domain for thenotification signal, and then, another notification signal (namely,notification signal “ΦX” in FIG. 19) is transmitted within the providedslot. As a result, a variation may be made in the method for taking thefixed slots (namely, table to be utilized). In other words, since theabove-described control operation is carried out, each of thecommunication systems can hold the plurality of tables, and therespective communication systems can utilize the plurality of tableswhile switching these plural tables.

FIG. 20 is one example as to a slot allocation table, namely indicatessuch a table which is utilized when the communication system “B” hastransmitted signals within the same control domains (in this example, itis so assumed that communication system “B” has two tables shown in FIG.16 and above example). Although tables are actually present in othercommunication systems, changed tables are described as to only thecommunication system “B” as a typical example. As indicated in FIG. 20,the communication system “B” uses only two pieces of slots (namely,slots “S2” and “S8”). Since such a control operation is carried out, itis possible to utilize such a table which is different from the table ofFIG. 16. It should also be noted that the table of FIG. 20 is not fixed,but is merely one example, and therefore, may be arbitrarily set. Inother words, in the table shown in FIG. 20, as compared with the tableof FIG. 16, the slots which the system “B” can utilize are deleted.However, a plurality of completely different tables (namely, tableshaving different meanings) may be formed, and these completely differenttables may be switched in response to a control signal. As only the usecondition with respect to the present invention, the same tables areheld in all of the communication systems, and the same table is utilizedby the respective communication apparatuses in accordance with thesignal of the control domain.

Although the above-described embodiments have exemplified such a casethat the respective communication systems alternately transmits thenotification signals, other notification signal transmitting methods maybe similarly employed by employing the table updating slot. Also, aplurality of table updating slots may be provided, and therefore aplurality of tables can be constructed.

As previously described, when the PLC modem 10 connected to the powerline 1A transmits the data, the PLC modem 10 transmits the controlsignal, receives the control signal, transmits the data signal, andreceives the data signal. These process operations are mainly carriedout by the main IC 11.

Even when plural sorts of communication apparatuses whose communicationsystems are different from each other are connected to the sharedtransmission channel, the present invention is usefully employed as acommunication method, a communication apparatus, a communication system,and the like, which can perform the following process operations: Thatis, while limits of delays in response to data which are tried to betransmitted by the respective communication apparatuses can besatisfied, signals can be transmitted in a higher efficiency by avoidingcollisions of signals. Also, the present invention is useful as such acommunication method, a communication apparatus, a communication system,and the like, which are capable of reducing processing workloads forallocating the slots executed by the communication apparatus in order toavoid the collisions of the signals.

This application is based upon and claims the benefit of priority ofJapanese Patent Application No. 2007-266950 filed on Oct. 12, 2007, thecontents of which are incorporated herein by reference in its entirety.

1. A communication apparatus which is capable of communicating based ona first communication system via a transmission channel to which anothercommunication apparatus communicating based on a second communicationsystem is capable of connecting, comprising: an integrated circuit; ahousing which includes the integrated circuit; a first connector whichis adapted for connecting the transmission channel provided on a firstside of the housing; an indicator which is provided on a second side ofthe housing; wherein the integrated circuit comprises: a transmitterwhich transmits a first notice including a first notification signalwhich is rotated by a first phase vector and a second notificationsignal which is rotated by a second phase vector within a firstnotification domain; a detector which detects a second noticetransmitted from the another communication apparatus within the secondnotification domain which is different from the first notificationdomain; and a controller which allocates a data transmission which istransmitted from the communication apparatus and a data transmissionwhich is transmitted from the another communication apparatus for atleast one of data transmission domains on the basis of the first noticeand the second notice.
 2. The communication apparatus according to claim1, wherein the first notification domain is allocated to the firstcommunication system and the second notification domain is allocated tothe second communication system.
 3. The communication apparatusaccording to claim 1, wherein a transmission order of the firstnotification signal and the second notification signal corresponds toone of the first communication system and the second communicationsystem.
 4. The communication apparatus according to claim 3, wherein thefirst notification signal and the second notification signal aretransmitted in order of the first notification signal and the secondnotification signal, the order of those notification signal correspondsto the first communication system.
 5. The communication apparatusaccording to claim 3, wherein the second notice including the firstnotification signal and the second notification signal, wherein thefirst notification signal and the second notification signal aretransmitted in order of the second notification signal and the firstnotification signal, the order of those notification signal correspondsto the second communication system.
 6. The communication apparatusaccording to claim 1, wherein the controller allocates the datatransmission domain in a predetermined allocation order on the basis ofthe first notice and the second notice.
 7. The communication apparatusaccording to claim 6, further comprising a memory for previously storingthe allocation order of the data transmission domain.
 8. Thecommunication apparatus according to claim 1, wherein the transmissionchannel is a power line which is provide an alternating current, whereinthe first notification domain and the second notification domain areallotted on the basis of zero cross points of the alternating current.9. The communication apparatus according to claim 1, wherein the firstnotification domain and the second notification domain are allottedperiodically on the basis of a predetermined interval.
 10. Thecommunication apparatus according to claim 1, wherein the indicatorprovides a light-emitting element.
 11. The communication apparatusaccording to claim 1, wherein the first side is opposite for the secondside.
 12. The communication apparatus according to claim 1, furthercomprising a second connector is provided on the first side and adaptedfor connecting a communication cable.
 13. The communication apparatusaccording to claim 1, wherein the first side provides a flat surface.14. The communication apparatus according to claim 1, wherein the secondside provides a flat surface.
 15. The communication apparatus accordingto claim 1, wherein the first side provides a first flat surface, thesecond side provides a second flat surface, and wherein the first flatsurface is substantially parallel to the second flat surface.
 16. Acommunication apparatus which is capable of communicating based on afirst communication system via a transmission channel to which anothercommunication apparatus communicating based on a second communicationsystem is capable of connecting, comprising: an integrated circuit; ahousing which includes the integrated circuit; at least three indicatorswhich are provided on one side of the housing; wherein the integratedcircuit comprises: a transmitter which transmits a first noticeincluding a first notification signal which is rotated by a first phasevector and a second notification signal which is rotated by a secondphase vector within a first notification domain; a detector whichdetects a second notice transmitted from the another communicationapparatus within the second notification domain which is different fromthe first notification domain; and a controller which allocates a datatransmission which is transmitted from the communication apparatus and adata transmission which is transmitted from the another communicationapparatus for at least one of data transmission domains on the basis ofthe first notice and the second notice.
 17. The communication apparatusaccording to claim 16, wherein the three indicators are located on aline.
 18. The communication apparatus according to claim 16, wherein thethree indicators include a first indicator, a second indicator and athird indicator, and wherein the second indicator is located between thefirst indicator and the third indicator.
 19. A communication apparatuswhich is capable of communicating based on a first communication systemvia a transmission channel to which another communication apparatuscommunicating based on a second communication system is capable ofconnecting, comprising: an integrated circuit; a housing which includesthe integrated circuit; wherein the integrated circuit comprises: atransmitter which transmits a first notice including a firstnotification signal which is rotated by a first phase vector and asecond notification signal which is rotated by a second phase vectorwithin a first notification domain; a detector which detects a secondnotice transmitted from the another communication apparatus within thesecond notification domain which is different from the firstnotification domain; and a controller which allocates a datatransmission which is transmitted from the communication apparatus and adata transmission which is transmitted from the another communicationapparatus for at least one of data transmission domains on the basis ofthe first notice and the second notice wherein the housing is providedwith only one connector which is adapted for connecting a communicationcable.
 20. The communication apparatus according to claim 18, whereinthe connector is adapted for connecting an Ethernet cable.